The present invention relates generally to bearing cages for use in rotating machinery and, more particularly, to bearing cages molded of a polymer.
Bearing cages are conventionally used in ball and roller bearings to retain and separate rolling elements (rollers, needles or balls) in predetermined relative positions. The bearing cages lie between inner and outer bearing races.
In certain applications, bearing cages are exposed to relatively difficult conditions that limit the useful life of the bearing cages or require the use of complex and expensive construction. One such application is in the needle bearing assembly for a crank of a two-cycle engine such as, for example, an outboard motor.
In such an application, the needle bearing assembly is exposed to high loads generated by combustion pressure, inertia of the parts, and centrifugal force. This application is so severe that a special high precision bearing cage made of silver-plated steel, is generally used. The silver is believed to act as a lubricant, at least during a break-in period of the bearing.
There are numerous disadvantages to the above-described bearing cage. The high precision requires numerous steps for manufacture, such as piercing, heat treating, grinding, and chemical finishing. The initial cost of tooling is very high, and the chemical by-products produced during manufacture result in environmental problems of disposal. In addition, because of the many operations which must be performed, the time for manufacture of such bearing cages is long. Thus, a larger than desired inventory of work in process must be maintained. The large number of operations, combined with the required precision, may result in high labor costs or a relatively high scrap rate. And, the required silver substantially adds to the cost.
The foregoing illustrates limitations known to exist in present bearing cages. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.